GRB 180325A
GCN Circular 22532
Subject
GRB 180325A: Swift detection of a burst with an optical counterpart
Date
2018-03-25T02:04:12Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Troja (NASA/GSFC/UMCP), A. D'Ai (INAF-IASFPA), V. D'Elia (ASDC),
J. A. Kennea (PSU), S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), M. H. Siegel (PSU)
and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 01:53:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180325A (trigger=817564). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 157.432, +24.439 which is
RA(J2000) = 10h 29m 44s
Dec(J2000) = +24d 26' 21"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a ~10 second
FRED peak (~3000 counts/s) which is followed by brighter peak
which reaches a maximum of ~11000 counts/sec (15-350 keV), at ~81
after the trigger, for a total duration of ~120 seconds.
The XRT began observing the field at 01:54:16.2 UT, 73.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 157.4281, 24.4627 which is equivalent to:
RA(J2000) = +10h 29m 42.74s
Dec(J2000) = +24d 27' 45.7"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 86 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 10:29:42.59 = 157.42746
DEC(J2000) = +24:27:48.5 = 24.46347
with a 90%-confidence error radius of about 0.76 arc sec. This position is 3.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.45 with a 1-sigma error of about 0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02.
We note that the second peak seen by BAT occurs during the
early UVOT and XRT images, so these sample the prompt GRB
emission.
Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular 22534
Subject
GRB 180325A: prompt LT observations
Date
2018-03-25T03:05:01Z (7 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath),
A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU) on behalf of a large
collaboration report:
The 2-m Liverpool Telescope automatically began observing Swift GRB
180325A (Troja et al. GCN 22532) on March 25, 01:55:25 UT (143 seconds
since the GRB trigger time) with the RINGO3 polarimeter and the IO:O
camera in the SDSS-R filter. We clearly detect the optical afterglow
(Troja et al.) with the following magnitude:
Mid Time from GRB� � Exposure������������ Filter������������ Magnitude (AB)
(min)�������������������������� (s)
-------------------------------------------------------------
35.1���������������������������� 6x10�������������������� SDSS-R������������ 19.02 +- 0.05
-------------------------------------------------------------
as calibrated against nearby SDSS objects.
GCN Circular 22535
Subject
GRB 180325A: NOT redshift
Date
2018-03-25T03:33:36Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
K. E. Heintz (Univ. Iceland and DAWN/NBI), J. P. U. Fynbo (DAWN/NBI), D.
Malesani (DAWN/NBI and DARK/NBI), report on behalf of a larger
collaboration:
We observed the optical counterpart of GRB 180325A (Troja et al., GCN
22532; Guidorzi et al., GCN 22534) with the 2.5-m Nordic Optical
Telescope (NOT) equipped with ALFOSC, starting at 02:02:30 UT on 25
March 2018. We obtained 3x100 s in the r-band and measure a magnitude of
m(r) = 18.61 +/- 0.03 mag at a mean post-explosion epoch of 11 minutes.
The calibration was performed using local Pan-STARRS stars in the GRB
field. This apparent magnitude is not corrected for foreground extinction.
We subsequently obtained spectroscopy for a total of 3x600 s, using
grism #4 and covering the wavelength range 3650-9450 AA. In our
low-resolution spectrum we identify several absorption features,
including Mg II, Fe II, Al II, C IV, Si II at a common redshift of z =
2.25. The 2175 AA bump is clearly visible at this redshift. We also note
the presence of a strong intervening system at z = 2.04, as revealed by
Mg II and Fe II absorption features.
Further observations are in progress.
GCN Circular 22536
Subject
GRB 180325A: prompt REM optical/NIR detection
Date
2018-03-25T03:50:18Z (7 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D'Avanzo, A. Melandri, S. Covino, D. Fugazza (INAF/OAB) report on behalf of the REM team:
We observed the field of the GRB 180325A (Troja et al., GCN 22532) with the 60-cm robotic telescope REM located at the La Silla Observatory (Chile).
The observations started on 25-03-2018 at 01:53:52 UT, 50s after the burst, and were carried in the g, r, i, z, J, H and K bands.
A preliminary analysis shows that the optical counterpart (Troja et al., GCN 22532; Guidorzi et al. GCN 22534; Heintz et al. GCN 22535) is well detected
and at a mid time of 123 seconds after the burst it was:
r = 17.2 +/- 0.2 (AB)
H = 12.7 +/- 0.1 (Vega)
Magnitudes are calibrated against the SDSS (optical) and 2MASS (NIR) catalogues.
GCN Circular 22537
Subject
GRB 180325A: RATIR Optical Observations
Date
2018-03-25T06:01:31Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:
We observed the field of GRB 180325A (Troja et al., GCN 22532) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on
the 1.5m Harold Johnson Telescope at the Observatorio Astron��mico
Nacional on Sierra San Pedro M��rtir from 2018/03 25.12 to 2018/03 25.23
UTC (1.02 to 3.67 hours after the BAT trigger), obtaining a total of
1.47 hours exposure in the r and i bands and hours exposure in the Z, Y,
J, and H bands.
For a source within the Swift-XRT error circle, in comparison with the
SDSS DR9 catalog, we obtain the following detections:
r = 19.79 +/- 0.02
i = 19.38 +/- 0.01
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 22538
Subject
GRB 180325A: Optical Photometry with SLKT
Date
2018-03-25T06:42:44Z (7 years ago)
From
Peter Garnavich at U of Notre Dame <pgarnavi@nd.edu>
C. Littlefield and P. Garnavich (Notre Dame) report:
We observed the field of GRB 180325A (GCN 22532) with the
0.8-m Sarah L. Krizmanich Telescope at the University of
Notre Dame. Unfiltered CCD images were obtained
under hazy conditions beginning 1.5 hours after the
burst. We calibrated the afterglow in SDSS-r using a
nearby star in the Pan-STARRS catalog and constructed
the following light curve:
DateAge SDSS-r err
(UT) (hours)
March 25.1403 1.483 19.29 0.14
March 25.1626 2.018 19.52 0.18
March 25.227 3.564 20.1 0.3
Based on SDSS-r magnitudes reported by Heintz et al.
(GCN 22535) and Guidorzi et al. (GCN 22534), we obtain
a rather shallow power-law decay index of 0.31+/-0.05
between 0.5 hours and 2 hours after the burst.
GCN Circular 22539
Subject
GRB 180325A: Enhanced Swift-XRT position
Date
2018-03-25T07:43:32Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 2783 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 180325A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 157.42735, +24.46361 which is equivalent
to:
RA (J2000): 10h 29m 42.56s
Dec (J2000): +24d 27' 49.0"
with an uncertainty of 1.5 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 22540
Subject
GRB 180325A: Swift-XRT refined Analysis
Date
2018-03-25T12:09:56Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri
(INAF-OAB), P. D'Avanzo (INAF-OAB), A. Tohuvavohu (PSU), S. J. LaPorte
(PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester) and E. Troja report on behalf of the Swift-XRT team:
We have analysed 6.0 ks of XRT data for GRB 180325A (Troja et al. GCN
Circ. 22532), from 61 s to 29.3 ks after the BAT trigger. The data
comprise 329 s in Windowed Timing (WT) mode (the first 10 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 22539).
The late-time light curve (from T0+4.8 ks) can be modelled with a
power-law decay with a decay index of alpha=2.02 (+0.09, -0.08).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.60 (+/-0.09). The
best-fitting absorption column is 1.7 (+0.6, -0.5) x 10^22 cm^-2, at a
redshift of 2.25, in addition to the Galactic value of 1.3 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.85 (+/-0.09) and a best-fitting absorption column of 1.3 (+/-0.4)
x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.2 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.3 x 10^20 cm^-2
Intrinsic column: 1.3 (+/-0.4) x 10^22 cm^-2 at z=2.25
Photon index: 1.85 (+/-0.09)
If the light curve continues to decay with a power-law decay index of
2.02, the count rate at T+24 hours will be 7.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.5 x
10^-13 (2.9 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00817564.
This circular is an official product of the Swift-XRT team.
GCN Circular 22541
Subject
GRB 180325A: D50 early optical follow-up
Date
2018-03-25T13:20:11Z (7 years ago)
From
Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek@asu.cas.cz>
Jan Strobl, Martin Jelinek and Rene Hudec (ASU CAS Ondrejov)
report
We observed the field of the Swift GRB 180325A (Troja et al., GCNC 22532)
with the 0.5m telescope D50 in Ondrejov (Czech Republic), starting at
01:53:47.1 UT, i.e. 44.3s after the trigger.
The observation consisted of a series of 10 s unfiltered exposures,
covering the peak of the optical emission at mag ~16.3. The maximum seems
to be somewhat delayed with respect to the bright peak in gamma-rays.
This message can be cited.
GCN Circular 22542
Subject
GRB 180325A: TAROT Calern observatory optical observations
Date
2018-03-25T14:36:31Z (7 years ago)
From
Alain Klotz at IRAP-CNRS-OMP <Alain.Klotz@free.fr>
Klotz A., Noysena K., Atteia J.L. (CNRS-OMP-IRAP),
Boer M., Eymar L. (CNRS-ARTEMIS),
Gendre B. (UVI - Etelman Obs.) report:
We imaged the field of GRB 180325A detected by SWIFT
(trigger 817564) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.
The observations started 26s after the GRB trigger
(14s after the notice). The elevation of the field decreased
from 37 degrees above horizon and weather conditions
were excellents.
We detect clearly the optical transcient (OT) reported by
Troja et al. (GCN 22532), Guidorzi et al. (GCN 22534),
Heintz et al. GCN 22535), D'Avanzo et al. (GCNC 22536),
Watson et al. (GCNC 22537), Garnavich et al. (GCNC 22538),
Strobl et al. (GCNC 22541).
The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We detect the OT at a magnitude of:
t0+26s to t0+86s : r(AB) = 17.2 +/- 0.3
It is important to notice that a bright gamma flash in
Swift-BAT data occured between 70 and 92 seconds. We
do not detect any significant optical flux increase
during the range 70 to 86 seconds of the first TAROT
exposure.
After an overhead time of 13 seconds the second image
of 30s exposure in tracking mode started 99 seconds
after the trigger. In this image the OT has brightened
by about 1 magnitude. The third image shows a rapid
decrease of 1 magnitude compatible with a decay index
of about 3 followed by a mean decay of 0.45 until
1.7 hour after the trigger confirming the small decay
value published by Littlefield and Garnavich (GCNC 22538).
The photometric analysis of the TAROT images are given:
t1(h) t2(h) r(AB) 1sig
0.0277 0.0361 16.24 0.09
0.0391 0.0474 17.22 0.20
0.0504 0.0815 17.68 0.19
0.0843 0.1093 18.02 0.30
0.2062 0.2872 18.56 0.30
0.2951 0.4364 18.78 0.39
0.4392 1.1843 18.94 0.22
1.2400 1.6746 19.26 0.36
Magnitudes were estimated with the nearby star
NOMAD-1 1144-0181799 R=14.440 (V-R)=0.65, converted into
r(AB) system and are not corrected for galactic dust extinction.
Note that the TAROT light curve is compatible with an
optical flash occuring with a lag of 20 +/- 10 seconds
after the bright gamma emission peak as mentioned
by Strobl et al. (GCNC 22541).
GCN Circular 22543
Subject
GRB 180325A: Global MASTER-Net OT prompt observations
Date
2018-03-25T15:05:51Z (7 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E.Gorbovskoy, N.Tyurina, V.Kornilov, D.Zimnukhov, V.Vladimirov,
A.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.Chazov, D. Kuvshinov
(Lomonosov Moscow State University, SAI),
R.Podesta, C.Lopez, F. Podesta
(Observatorio Astronomico Felix Aguilar (OAFA),National University of San
Juan, Argentina),
H. Levato, C. Saffe
(Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE),
San Juan, Argentina),
R. Rebolo, M. Serra-Ricart, G.Israelyan
(The Instituto de Astrofisica de Canarias),
D.Buckley, S. Potter
(South African Astronomical Observatory),
O.Gres, N.M.Budnev
(Irkutsk State University),
A. Tlatov, V.Senik, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory)
V.Yurkov, A.Gabovich, Yu.Sergienko
(Blagoveschensk Educational State University, Blagoveschensk),
MASTER-OAFA and MASTER-IAC automatically pointed to GRB 180314A (Eleonora
Troja et al. GCN 22532) with optical transient detection by MASTER
auto-detection system.
We confirm Swift, LT, NOT, REM, RATIR, SLKT, D50 GROND OT (GCN 22532,
22534, 22535, 22536, 22537, 22538, 22541) but observed before.
MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in OAFA (Argentina,http://oafa.master.sai.msu.ru:49001/) was
pointed to the GRB180325.08 38 sec after
trigger time at 2018-03-25 01:53:40 UT. On our second
(20s exposure) set robot automaticaly found 1 optical transient within
SWIFT error-box (ra=157.429 dec=24.4389 r=0.05) brighter then 16.7 .
T-Ttrig Date Time Expt. Ra Dec Mag
-------|-------------------|-------|-----------------|---------------|-------
88 2018-03-25 01:54:31 20 ( 10h 29m 42.7s , +24d 27m 49.3s) 16
The 5-sigma upper limit has been about 17.3mag
====================================================================
The observations made on zenit distance = 58 degrees, galaxy latitude b =
59 degree. The moon (55 % bright part) is 25 degrees above the horizon.
The distance between moon and object is 53
The sun altitude is -40.3 degree.
The object can be observed till 2018-03-25 07:53:41 UT.
MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru)
located in IAC (Tenerife, Tejde Observatory) was pointed to the
GRB180325.08 63 sec after trigger time
at 2018-03-25 01:54:09 UT. On our second
(20s exposure) set robot automaticaly found 1 optical transient within
SWIFT error-box (ra=157.429 dec=24.4386 r=0.05) brighter then 17.0.
T-Ttrig Date Time Expt. Ra Dec Mag
-------|-------------------|-------|-----------------|-----------------|-------
119 2018-03-25 01:55:01 20 ( 10h 29m 42.6s , +24d 27m 48.3s) 16.50
The 5-sigma upper limit has been about 17.5 mag
The message may be cited.
====================================================================
The observations made on zenit distance = 34 degrees, galaxy latitude b =
59 degree.
The moon (55 % bright part) is 6 degrees above the horizon. The distance
between moon and object is 53
The sun altitude is -58.3 degree.
The object can be observed till 2018-03-25 06:24:39 with good limit.
This message can be cited.
GCN Circular 22544
Subject
GRB 180325A: GROND observations
Date
2018-03-25T17:51:03Z (7 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
T. Schweyer (MPE), and D. A. Kann (HETH/IAA-CSIC) report:
We observed the field of GRB 180325A (Swift trigger 817564; E. Troja et
al., GCN #22532) simultaneously in g'r'i'z'JHK with GROND (Greiner et
al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La
Silla Observatory (Chile).
Observations started at 02:53 UTC on March 25, 1.0 hours after the GRB
trigger. They were performed at an average seeing of 1".5 and at an
average airmass of 1.7.
We clearly detect the NIR/optical transient of GRB 180325A within the
enhanced XRT position (J. P. Osborne et al., GCN #22539), in agreement
with the optical transient detected by UVOT (E. Troja et al., GCN
#22532).
Based on 7 minutes of exposure centered around 03:30 UTC, we measure the
following magnitudes (all in AB system).
g' = 20.45 +/- 0.03 mag
r' = 19.57 +/- 0.02 mag
i' = 19.18 +/- 0.02 mag
z' = 18.30 +/- 0.02 mag
J = 17.42 +/- 0.02 mag
H = 16.85 +/- 0.02 mag
K = 16.34 +/ 0.03 mag
Given magnitudes are calibrated against SDSS in g'r'i'z' and 2MASS field
stars in JHK, and are not corrected for the Galactic foreground
extinction corresponding to a reddening of E_(B-V)= 0.015 in the
direction of the burst (Schlafly & Finkbeiner 2011).
We acknowledge the excellent support from the TiO and the current
observer at the 2.2m in La Silla, Angela Hempel and Victor Marian.
GCN Circular 22545
Subject
GRB 180325A, Swift-BAT refined analysis
Date
2018-03-25T22:01:01Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF/USRA),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+500 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180325A (trigger #817564)
(Troja et al., GCN Circ. 22532). The BAT ground-calculated position is
RA, Dec = 157.416, 24.461 deg which is
RA(J2000) = 10h 29m 39.9s
Dec(J2000) = +24d 27' 39.7"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 89%.
The mask-weighted light curve shows two separate pulses. The first pulse
starts and peaks at ~T0, and ends at ~T+10 s. The second brighter pulse
starts at ~T+70 s, peaks at ~T+80 s, and ends at ~T+110 s. T90 (15-350 keV)
is 94.1 +- 1.5 sec (estimated error including systematics).
The time-averaged spectrum from T-0.0 to T+107.9 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.18 +- 0.05. The fluence in the 15-150 keV band is 6.5 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+80.75 sec in the 15-150 keV band
is 9.4 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/817564/BA/
GCN Circular 22546
Subject
Konus-Wind observation of GRB 180325A
Date
2018-03-26T09:41:07Z (7 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, R.Aptekar, M. Ulanov, D. Svinkin,
A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 180325A (Swift-BAT trigger 817564:
Troja et al., GCN 22532; Lien et al., GCN 22545)
triggered Konus-Wind at T0=6866.876 s UT (01:54:26.876)
The burst light curve shows a single pulse,
which started at ~T0-1 s and peaked at ~T0+1.7 s.
The total duration of the burst is ~10 s.
The emission is seen up to ~7 MeV.
As observed by Konus-Wind, the burst had a fluence of
(1.9 �� 0.3)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+1.728, of (8.2 �� 1.3)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+7.424 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.50 (-0.19,+0.21),
the high energy photon index beta = -2.65 (-1.06,+0.31),
the peak energy Ep = 306 (-39,+50) keV,
chi2 = 99/92 dof.
Assuming the redshift z=2.25 (Heintz et al., GCN 22535)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, and Omega_Lambda = 0.7,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~2.3x10^53 erg,
the peak luminosity L_iso is ~3.2x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,z, is ~995 keV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180325_T06866/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 22549
Subject
GRB 180325A: Swift/UVOT Detection
Date
2018-03-26T17:07:59Z (7 years ago)
From
Frank Marshall at Swift/UVOT <marshall@milkyway.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180325A
82 s after the BAT trigger (Troja et al., GCN Circ. 22532).
A fading source consistent with the enhanced XRT position
(Osborne et al. GCN Circ. 22539)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 10:29:42.59 = 157.42744 (deg.)
Dec (J2000) = +24:27:48.6 = 24.46349 (deg.)
with an estimated uncertainty of 0.44 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 82 232 147 18.48 +/- 0.05
white 5039 5239 197 20.75 +/- 0.23
v 5450 5650 197 >18.8
b 4834 6385 309 >20.1
u 295 6265 353 >20.0
w1 5860 6060 197 >20.1
m2 5654 5854 197 >19.4
w2 5245 12343 980 >20.9
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22551
Subject
GRB 180325A: further NOT observations
Date
2018-03-26T23:43:36Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
Daniele Malesani (DAWN/NBI and DARK/NBI) and Johan P.U. Fynbo (DAWN/NBI) report on behalf of a larger collaboration:
We observed the optical afterglow of GRB 180325A (Troja et al., GCN 22532) using the Nordic Optical Telescope (NOT) equipped with the AlFOSC imaging camera. The seeing in our observations was not good, around 2". 4 and 2 exposures by 600 s were obtained in the R and I filters, respectively.
The afterglow was not detected in R, and marginally (if at all) in I. The following magnitudes were computed with respect to nearby Pan-STARRS reference stars, and are therefore in the AB system.
Time (UT) Time since GRB (hr) Filter Magnitude
-----------------------------------------------------
Mar 25.856 18.65 r >22.6
Mar 25.871 18.92 i 22.9 +- 0.3
These values are significantly fainter than the extrapolation based on the earlier measurements (Guidorzi et al., GCN 22534; Heintz et al., GCN 22535; D'Avanzo et al., GCN 22536; Watson et al., GCN 22536; Littlefield & Garnavich, GCN 22538; Strobl et al., GCN 22541; Klotz et al., GCN 22542; Lipunov et al., GCN 22543; Schweyer & Kann, GCN 22544) and indicate a break in the afterglow light curve.
GCN Circular 22555
Subject
GRB 180325A: VLT/X-shooter spectroscopic observations
Date
2018-03-27T21:30:43Z (7 years ago)
From
Paolo D'Avanzo at INAF-OAB <paolo.davanzo@brera.inaf.it>
P. D���Avanzo (INAF-OAB), J. Bolmer (ESO/MPE), V. D���Elia (ASI-SSDC), J. P. U. Fynbo (DAWN/NBI), K. E. Heintz (U. Iceland, DAWN/NBI), L. Izzo (HETH/IAA-CSIC), J. Japelj (API, U. Amsterdam), D. A. Kann (HETH/IAA-CSIC), D. Malesani (DAWN/NBI and DARK/NBI), J. Selsing (DARK/NBI), N. R. Tanvir (Univ. Leicester), T. Zafar (AAO), S. Campana (INAF-OAB), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), J. Hjorth (DARK/NBI), L. Kaper (Univ. Amsterdam), A. Melandri (INAF-OAB), A. Smette (ESO), report on behalf of the Stargate Consortium:
We observed the optical afterglow of GRB 180325A (Troja et al. GCN 22532) with the ESO VLT/X-shooter spectrograph, covering the wavelength range 3000-25000 AA. Spectroscopy started at 03:20:45 UT on 2018-03-25 (i.e., ~1.5 hr after the GRB) and consisted of 8 exposures of 600 s.
The spectrum exhibits a red continuum with several absorption features, including Ly-alpha and different metal and fine-structure lines, together with [OII], [OIII] and Halpha emission lines, all at a common redshift of z=2.248. At the same redshift, we also note the presence of a clear continuum depression corresponding to the 2175 AA bump. Finally, the spectrum shows the presence of a strong double intervening system at z = 2.041/2.043.
The above results are in agreement with the findings of Heintz et al. (GCN 22535).
We acknowledge the excellent support from the ESO staff, particularly Luca Sbordone, Jose Velasquez and Zahed Wahhaj in obtaining these observations.
GCN Circular 22557
Subject
GRB180325A: AstroSat CZTI detection
Date
2018-03-29T10:36:12Z (7 years ago)
From
Vidushi Sharma at IUCAA <vidushi@iucaa.in>
V. Sharma (IUCAA), V. Bhalerao (IIT-B), D. Bhattacharya (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data showed the detection of a long GRB 180325A, which was also detected by Swift (Troja E. et al., GCN 22532), Swift-BAT (Lien A. Y. et al., GCN 22454), Swift-XRT (Page K.L. et al., GCN 22540) and Konus-Wind (Frederiks D. et al., GCN 22546).
The source was clearly detected in the 40-200 keV energy range. The light curve shows single peak of emission at 01:54:23.0 UT, ~81 s after Swift-BAT trigger time. The measured peak count rate is 1093.8 cts/s above the background in combined data of four quadrants, with a total of 5294 cts. The local mean background count rate was 510.2 cts/s. Using cumulative rates, we measure a T90 of 15.7 s. In Preliminary analysis, we find that 495.2 compton events are associated with this event.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.
CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.